The first three operators in the first line of (REF ) follow from integrating out the VLQs at tree level, which yields the coefficients (in matrix notation) [1]}
\(\mathbf {C}_Q = \frac{\mathbf {Y}_Q \mathbf {Y}_Q^\dagger }{2 m_Q^2} \,, \qquad \mathbf {C}_u = - \frac{\mathbf {Y}_U \mathbf {Y}_U^\dagger }{2 m_U^2} \,, \qquad \mathbf {C}_d = - \frac{\mathbf {Y}_D \mathbf {Y}_D^\dagger }{2 m_D^2} \,.\) 
